The aim of the present study is to investigate whether curative chemoradiation of low rectal cancer is feasible, safe and effective in a multicenter study with results comparable to those of single center studies.

Results from previous studies indicate that a considerable fraction of patients with low rectal cancer can be cured by a combination of radiation and chemotherapy alone and thus be spared from operation.

Inclusion Criteria:

• Histopathologically verified adenocarcinoma of the rectum

• Planned abdominoperineal resection (APR) or ultralow resection

• Primary, resectable T1-T3, N0 tumor. N1 nodal disease is acceptable, if the positive lymph nodes are localized to the mesorectum at the level of the tumor.

• Distance from anal verge to lower edge of tumor ≤ 6 cm measured by rigid rectoscope

• Performance status 0-2

• Patient acceptance to collection of biopsies and blood samples for translational research

• Age ≥ 18 years

• Normal function of bone marrow as evaluated by

  • neutrophils ≥ 1.5 x 10^9/l
  • thrombocytes ≥ 100

• Normal function of liver

  • alanine aminotransferase (ALAT) < 2.5 x upper limit of normal
  • bilirubin < 2.5 x upper limit of normal

• Kidney function

  - Serum creatinine < 1.5 x upper limit of normal or measured glomerular filtration rate (GFR) > 30 ml/min

• Fertile women must present a negative pregnancy test and use secure contraceptives during and 3 months after treatment.

• Written and orally informed consent

Exclusion Criteria:

• Previous surgical treatment of the present cancer, including transanal excision of tumor.
• Other malignant disease within the past five years except basocellular skin cancer and carcinoma in situ cervicis uteri
• Distant metastases verified by imaging or biopsy
• Previous radiation treatment of the pelvis
• Pregnant or breastfeeding women

Patients with low rectal cancer (tumor located ≤ 6 cm from the anal verge) who are referred to the participating departments and who fulfill the inclusion criteria.